1. Field of the Invention
This invention is directed to a differential locking assembly, which may be manually actuated and which is specifically, but not exclusively, adaptable for use on a four wheel drive, off-road vehicle.
2. Description of the Related Art
A differential assembly, of the type found on motor vehicles, comprises a gear system which is generally structured to transfer power from a drive or propeller shaft to the output or drive axle shafts of the vehicle. The differential assembly typically incorporates a ring gear which is secured to a housing or carrier of the differential and rotatable therewith. Also the ring gear is disposed in intermeshing, driven engagement with the propeller or drive shaft. Torque or rotational force is transferred to the axle shafts and their and associated drive wheels. More particularly, the rotational or driving force is transferred from the drive shaft to the differential housing and eventually to the drive axles, which are splined to respectively disposed and rotationally interconnected side gears. The side gears are mounted within the differential housing and are rotationally interconnected by means of a spider gear assembly. The spider gear assembly typically comprises two spaced apart pinion gears, which are interconnected by a cross pin or like structure and which serve to rotationally interconnect each of the two side gears.
In operation, as the drive or propeller shaft rotates, it serves to rotate the ring gear which in turn rotates the differential housing to which the ring gear is securely attached. The two pinion gears, which define the spider gear assembly, rotationally interact with the two side gears, so as to rotate the output axle shafts and the drive wheels mounted on the outer ends thereof. When the motor vehicle is moving in a straight line direction, the ring gear and differential housing rotate together. In this straight line movement, the pinion gears of the spider gear assembly apply equal force to each of the side gears and their attached output axle shafts, as well as the respective wheels secured thereto. However, when the vehicle travels in a turning direction, the resistance against the rotation of one of the output axle shafts increases as the inner and outer wheels turn at different speeds. This difference in speed encourages the differential pinion gears of the spider gear assembly to rotate and turn the side gear on the axle encountering the increased resistance.
As generally described above, the structure and operation of a somewhat conventional differential serves an important purpose in the operation of a motor vehicle, especially when operating in a conventional, xe2x80x9con-roadxe2x80x9d environment. As set forth above, the use of the differential serves to transmit the driving torque from the drive shaft through the differential and apply such torque to either wheel substantially equally even though one wheel is rotating at a faster rate than the other, when the vehicle is involved in a turning maneuver. However, it is well recognized that in a number of situations it is highly desirable to lock the drive wheels of a vehicle so that they rotate synchronously. By locking the drive wheels of the vehicle to rotate at a synchronous speed, variations in traction of the drive wheels of the vehicle will not affect the rate of relative rotation between the drive wheels which are associated with the same axle. Therefore, the drive wheels associated with a common axle will rotate in unison even though there is variable traction, which normally causes slippage of one or other of the drive wheels.
It is well known that off-road vehicles, when encountering rough terrain, frequently have one or other of the drive wheels inadvertently disposed above or otherwise out of contact with the ground or surface over which the vehicle is traveling. The absence of a differential locking assembly in such situations would result in the free or non-contact wheel rotating while the opposite wheel, disposed in engaging relation with the surface, is absent rotational torque. Accordingly, there is a well recognized need and important use of differential locking assemblies capable of selectively locking the axle shafts of corresponding drive wheels, such that the wheels rotate synchronously regardless of their relative orientation or the amount of resistance being encountered.
Numerous attempts have been made to establish an efficient, durable, high strength locking assembly which may be applied to a variety of vehicles. Such differential locking assemblies are available for both manual and xe2x80x9cautomaticxe2x80x9d activation. In the latter category of automatic activation assemblies, sensing devices are incorporated within the differential so as to automatically activate an associated locking structure and thereby dispose the associated axle shafts into a synchronous, locked mode. While assumed to be functional for their intended purpose, such xe2x80x9cautomaticxe2x80x9d activation assemblies are not particularly applicable or desirable for use in the four wheel drive, xe2x80x9coff-roadxe2x80x9d vehicles, which are specifically designed and structured to travel over extremely rough terrain. In such an environment, the manual actuation of a differential lock is preferable and generally considered to be both more reliable and durable.
Accordingly, there is a significant need in the field of differential locking assemblies for a high strength, durable and consistently operative locking assembly which is particularly, but not exclusively, adaptable for use in off-road, four wheel drive vehicles. The design and structure of such an improved and preferred differential locking assembly should be such as to be readily adaptable for an xe2x80x9cafter marketxe2x80x9d application, such that off-road vehicles, of the type described above, can be easily adapted to include an improved differential locking assembly having all of the attributes which are necessary to endure the rigors of off-road operation.
The present invention is directed towards a locking assembly for the differential of a motor vehicle and is particularly, but not exclusively, adaptable for use on xe2x80x9coff-roadxe2x80x9d, vehicles of the type which are structured or modified to travel over extremely rough terrain. As a result of the vehicle operating in such a harsh environment, it is not uncommon for one of the drive wheels of an associated axle to be lifted or positioned out of contact with the ground or other surface over which the vehicle is traveling. In such instances, the operation of a conventional differential will deliver rotational torque or driving force to the wheel which is not in contact with the surface. For obvious reasons, such a situation is highly undesirable and will significantly affect the efficient and desired operation of the vehicle.
Accordingly, the present invention is directed towards a locking assembly which is preferably, but not exclusively, manually actuated so as to selectively dispose the locking assembly into a either a locked position or an unlocked position, at the will of the operator. When in the locked position, both drive wheels associated with a common axle will be locked so as to rotate in synchronous relation to one another, thereby overcoming the conventional operation of the differential.
More specifically, the differential locking assembly of the present invention is structured to function with cooperative components of a differential, such as, but not limited to the type produced and made commercially available by the Dana Corporation of Toledo, Ohio. As such, a differential housing or carrier has a ring-gear fixedly secured thereto so as to rotate therewith. Also in substantially conventional fashion, the ring gear is rotationally driven by its interconnection with the drive shaft of the vehicle. Such interconnection also serves to rotate the differential housing. Two side gears are mounted within the differential housing and normally rotate relative thereto. The side gears are secured in driving relation to co-extensive axle shafts of an axle assembly, wherein the outer end of each axle shaft is secured to a separate drive wheel. The inner end of each axle shaft is secured, by a splined engagement, with respective ones of the aforementioned side gears. A spider gear assembly, comprising spaced apart pinion gears and an interconnecting cross pin, serves to rotationally interconnect the side gears and is cooperatively structured therewith to define the operational workings of the differential.
Structural features of the differential locking assembly of the present invention include a locking member mounted on the differential housing so as to rotate therewith and move relative thereto, into and out of the aforementioned locked end unlocked positions. In addition, the locking assembly of the present invention includes a locking gear assembly which is disposed and structured to establish a locking interconnection of both of the axle shafts of an associated drive axle. As a result, both drive wheels of the associated drive axle are locked into synchronous rotation with one another regardless of their respective orientations relative to the ground or other surface over which the vehicle is traveling.
The aforementioned locking gear assembly is structured to be durable, strong, reliable and perform consistently, particularly in the harsh environment in which off-road vehicles are intended to operate. In order to provide such reliable and durable performance, the locking gear assembly includes a first locking gear integrally formed on an outer face of one of the side gears. The locking gear assembly also includes a second locking gear integrally formed on a corresponding or confronting surface or face of the locking member. As set forth above, the locking member is selectively positionable or slidable on the differential housing as it rotates therewith. Therefore, the first and second locking gears may be selectively disposed into intermeshing engagement with one another, as the differential housing rotates, to define the aforementioned locked position or selectively disposed out of engagement with one another to define the aforementioned unlocked position. Additional structural features, as set forth in greater detail hereinafter, are attributable to the first and second locking gears in order to assure their durability and consistently reliable performance under the aforementioned harsh operating conditions.
Other structural features incorporated within the differential locking assembly of the present invention include to a mounting assembly which movably supports the locking member on the differential housing so that it selectively moves relative thereto, between the aforementioned locked position and unlocked position. The mounting assembly comprises a plurality of transversely elongated cams of predetermined number, collectively arranged in a predetermined configuration so as to engage an equal number of correspondingly dimensioned and configured apertures formed in the locking member. Movable support of the locking member on the differential housing is thereby accomplished and failure and breakage due to stress placed on the locking member, such as when it is selectively disposed in the locked position, is significantly reduced or eliminated. The noticeable reduction in stress failures of the subject locking assembly is due, at least in part, to the equal distribution of forces which the mounting assembly may accommodate due its structure, disposition and cooperative engagement with both the differential housing and the locking member.
Another structural feature of the present invention is the inclusion of a positioning assembly which may be selectively activated to assume either the locked position or the unlocked position. It is well known in the structural design and operation of other locking assemblies to provide for either the manually or xe2x80x9cautomaticxe2x80x9d activation thereof. Under certain pre-established operating conditions, conventional differential lockers will be automatically activated to lock the drive wheels of a vehicle into synchronous rotation with one another. Typically, such automatic activation assemblies include hydraulic, pneumatic and/or electric modes of operation. While such automatic activation assemblies are generally considered to be operative for their intended function, they frequently are not designed to effectively operate with off-road, four wheel drive vehicles. Therefore, the differential locking assembly of the present invention is specifically, but not exclusively, adaptable for manual activation. Therefore, the positioning assembly of the present invention preferably comprises a manual shifter mechanism, connected by a drive cable, of the type well known and used extensively in modern day motor vehicles, to a fork-type shifter. The fork shifter selectively engages the locking member and moves it in a direction which is coaxial to the axis of rotation of the differential housing and the corresponding side gear. Operative interconnection of the manual shifter, located within the passenger compartment of the vehicle, and the locking member by the aforementioned drive cable, serves as a reliable and efficient structure for selectively positioning the locking member. The locking member need only be moved a relatively small distance relative to the one side gear on which the first locking gear is formed, in order to position the locking member into the aforementioned locked position. In addition, a plurality of biasing springs are disposed between the differential housing and the locking member so as to normally bias the locking member and the first and second locking gears, as set forth above, out of engagement with one another or into the unlocked position. Certain mechanical linkages associated with the manual shifter readily overcome this biasing force allowing the locking member to be easily disposed into the locked position, as described.
Therefore, the differential locking assembly of the present invention is preferably, but not exclusively, manually actuated for disposition in either a locked position or an unlocked position and includes specific structural components that assure durability, reliability and consistent operational characteristics, especially when the vehicle is operating under the extremely harsh environment of off-road conditions.
These and other objects, features and advantages of the present invention will become more clear when the drawings as well as the detailed description are taken into consideration.